NBC’s Kristen Welker asked Trump, “don’t you need to uphold the Constitution of the United States as president?” Trump answered, “I don’t know.” What!? At both inaugurations Trump swore an oath to “preserve, protect and defend the Constitution of the United States.” So legal duty aside, Trump swore an oath to uphold the Constitution. But yes, the U.S. Constitution, Art II §1, requires this oath, and thus the duty:
“Before he enter on the Execution of his Office, he shall take the following Oath or Affirmation:– I do solemnly swear (or affirm) that I will faithfully execute the Office of President of the United States, and will to the best of my Ability, preserve, protect and defend the Constitution of the United States.”